The present invention relates in general to the art of earth boring and more particularly to a rotary rock bit with an improved bearing system. The present invention is especially adapted for use on that type of rotary rock bit popularly known as a three cone bit; however, its use is not restricted thereto and the bearing system of the present invention can be used in other earth boring bits wherein an improved bearing system is required.
A three cone rotary rock bit is adapted to be connected as the lower member of a rotary drill string. As the drill string is rotated the bit disintegrates the formations to form an earth borehole. The three cone rotary rock bit includes three individual arms that extend angularly downward from the main body of the bit. The lower end of each arm is shaped to form a bearing pin or journal. A rolling cone cutter is mounted upon each bearing pin (or journal) and adapted to rotate thereon. The cone cutters include cutting structure on their outer surface that serves to disintegrate the formations as the bit is rotated.
A rotary rock bit must operate under very severe environmental conditions and the size and geometry of the bit is restricted by the operating characteristics. At the same time, the economics of petroleum production demand a longer lifetime and improved performance from the bit. In attempting to provide an improved bit, new and improved materials have been developed for the cutting structure of the cone cutters thereby providing a longer useful lifetime for the cutters. This has resulted in the bearing system being the first to fall during the drilling operation. Consequently, a need exists for an improved bearing system to extend the useful lifetime of the bit.